[dlacouture]

Well, Pentax did a great job with those legacy lenses, but why did they stop halfway???
After some considerate thoughts about it, here are some proposals for an improved support of these old lenses with our pentaxes... Best thing yet, they could be implemented entirely by firmware!

Please note that these will in no way change the current behavior of PK-A lenses in Av or M modes, or PK-M/m42 lenses in M mode!

EDIT : The Poll is here!!!

Note: Custom functions indicated here are those for the K7 camera.
Note: m42 and PK-M lenses will be hereafter referred to as legacy lenses.
Note: A, F, FA, DA lenses will be hereafter referred to as PK-A lenses.
Note: a PK-A lens with the aperture ring set manually will be considered as a PK-m lens in the following proposals, as it`s behavior is then identical.

The current limitations with these legacy lenses are that :
1 - Av mode is not functional with PK-m lenses when the aperture selected is not the widest one.
2 - P-TTL is not available with legacy lenses.
3- Trap-focus is not available with legacy lenses.

1 - PK-m Av mode

The following proposals will enable Av mode on PK-M lenses, without any impact on m42 and PK-A current Av mode behaviors, or the PK-m current handling in M mode.
The choice between the two behaviors could be made via additional choices under custom function #37 "Using Aperture Ring", if ever Pentax decide to implement one or both.
Additionally, they will enable full P-TTL support with these legacy lenses (more on that later!).
For these two proposals, we start from the principle that the camera considers it has a legacy lens attached when the "A/M" pin (3rd pin counterclockwise on the camera mount) is not shorted.

1st Proposal:

* always stop-down a legacy lens :
-> the camera aperture actuator should be moved in its "fully stopped-down" position.
-> the lens will then react as a preset aperture lens (m42).
-> Note: when changing PK-A lenses with the camera still on, the actuator will thus move in this position while the lenses are not locked.

* Metering would be active for the standard time (as defined in the "Meter operating time" custom function #4)

* Upon shutter full press, the P-TTL metering flash would thus occur with the lens already stopped-down (see below).

* A press on DoF preview should open the lens, by moving the aperture actuator to its "full-open" position.


2nd Proposal:

* stop-down a legacy lens on shutter half-press only :
-> the camera aperture actuator should first be moved in its "fully stopped-down" position.
-> a small additional delay could be added here to allow for complete stop-down for slowly reacting lenses.
-> the camera could then meter the scene.

* Metering would be active only during the shutter half-press duration.

* Upon shutter full press, the P-TTL metering flash would thus occur with the lens already stopped-down (see below).

* DoF preview button behavior is not changed compared to its current implementation : it will stop-down the lens to the manually selected aperture.

2 - P-TTL support for m42 and PK-m


Some simple reasonings show that aperture and focus distance information can be left unknown, while still allowing full P-TTL features (wireless included).
Extensive tests done with m42 lenses also demonstrate this to be true : if the camera is tricked into thinking it has a wide-open A lens instead of a m42 lens (whatever aperture is actually set on this lens), then P-TTL is fully functional, for whatever fictional aperture you tricked the camera with!
So, the above proposals do indeed enable P-TTL with all legacy lenses in Av mode, even with the actual aperture unknown to the camera : as the metering flash would now happen while the lens is already stopped down (in both proposals), so an accurate reading can be obtained.

Note : P-TTL support in M mode with legacy lenses could also be made available by first stopping down the lens, then fire the metering burst, with a slight delay to allow full closure of the aperture with slow lenses.

3 - Catch-in Focus (custom function #35) with Legacy lenses

PK-m and m42 manual lenses could be supported by removing the mount's electrical contacts check.
Currently, there is a restriction preventing the use of legacy lenses with this Catch-in Focus feature by checking that some contact pins are shorted by the lens. This check is used for this feature only, and is not used by any other feature!
Removing this check would not hamper the current behavior with PK-A lenses, and will enable this feature with legacy lenses.

3bis - Catch-in Focus (custom function #35) with ALL lenses (legacy, F ,FA ,DA ,...)

Now, when enabled, an additional activation mode could be made available when the body is set to MF, by using the AF button (with all lenses types : m42, M, A, F, FA, and DA). Currently, AF button has no use in MF mode.
So, in MF, as long as the user presses the AF button, the body should wait for a focus confirm before taking a picture, and this for whatever lens is attached.

What do you think about these?

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Last edited by dlacouture; 05-07-2010 at 08:50 AM.

[Ira]

Pentax wants to sell NEW lenses.

It's a profit thing.

[dlacouture]

Then why spending time allowing a backward compatibility?
Why advertising it?
And, finally, why not changing the lens mount, a la Canon?

In the end, I don't think they will sell more lenses by doing a half-baked compatibility.
They know as well as us that:
1- only enthusiasts will use their manual lenses no matter what,
2- they are only a tiny part of the crowds,
3- they are in a "from my dead cold hands" mindset about their manual lenses.

And to be real : I love my old manual lenses, but that doesn't prevent me to buy those cool AF lenses I have.
Those dedicated enough to photography to use those old lump of glass have also enough dedication to buy those brand new lenses they need.

On the other hand, the average Joe will buy brand new AF lenses anyway, and he represents the real marketing target...

[ytterbium]

Show me a new a brand new 50/1.7. Or even better - 28/2.

If i need the extra stop in a nice package, some 2.8 wont make me happy. Neither will a barrel sized 1.4.

Which of the o-so-great DA* lenses have metal barrel?

I sold manual one and got F version because of the AF, but exposure accuracy was also a big reason. For some people this might be the only reason, so they go for A lenses.

How does this increases new lens sales? Except that it narrows choice for "all those lenses", making some of them overpriced and in some way defeating the whole point of this legacy support as a feature.
If there is such feature, just put the FEW damn LINES OF CODE to make it right. It won't change much in the sales, but people who actually use it will be a whole lot more satisfied and much more loyal customers.
Currently the support is more like an inherited feature, because of the same mount and way camera systems operate - not a well tought and much planed feature, except for the SR FL input.

P.S. You should have included some sort of poll, to see how many people care for better legacy support, how many of us are more or less fine the way it is and how many dont know/care.

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Last edited by ytterbium; 05-07-2010 at 08:03 AM.

[Ira]

I hear what you're both saying, but companies just don't think that way.

Anyway, just look at my lens list and you'll see that I'll benefit from ANY improvements to manual lens use. And admittedly, the long thread scared me, and I didn't read it fully.

Which I'll do right now.

[GeneV]

I really like the idea of the half-press for stopping down the manual lens. Pentax keeps moving the green button around just enough to be confusing. It seems to me that this could be implemented in firmware.

[Ira]

#3: I can short out the contacts with aluminum tape on the base of the lens.

[Jasvox]

Perhaps when/if Pentax releases a FF body, then it will address these concerns?

Jason

[macTak]

For the second proposal, there is a drawback. The light available to the AF system will be reduced as one stops down, so that focus confirmation through the green hexagon will not work as well (not to mention catch-in focus) in stopped down/darker situations.

I would simply love the ability to annotate in EXIF the aperture used. That could be easily done via a custom function.

[dlacouture]

For the second proposal, there is a drawback. The light available to the AF system will be reduced as one stops down, so that focus confirmation through the green hexagon will not work as well (not to mention catch-in focus) in stopped down/darker situations.

Well, it would be a problem for the first proposal as well, actually...
In both proposals, the lens is stopped down while doing the half-press (or when doing a full press with catch-in focus enabled).

I'll try this to see if and when it's a real problem for the AF system.

[Eruditass]

#3: I can short out the contacts with aluminum tape on the base of the lens.

Yes, but this isn't really fun to do, now is it?

After taking on and off a couple lenses, the tape and foil I put there starts to get messed up.

[pasipasi]

Uncripple the mount, thus allowing the camera body to know what aperture you're using. Solves every problem. I would have been ready to pay premium for that. Nikon has better vintage lens support here. And there I went.

[boriscleto]

Uncripple the mount, thus allowing the camera body to know what aperture you're using. Solves every problem. I would have been ready to pay premium for that. Nikon has better vintage lens support here. And there I went.

Only on the D300S/D700/D3S. The consumer cameras hardly support vintage lenses at all.

[alohadave]

I can do Trap Focus with a K/M lens on my K100D Super with no problems now. No tricks required.

[Lowell Goudge]

Aside from the title of this post, there are some errors that need to be corrected.

First of all, you cannot consider SMC and SMC-M lenses as the same as M42 lenses and call them both legacy lenses (although they are as far as pentax is concerned)

origonal K mount lenses all short pin 7 of the mount, which allows for focus confirmation and trap focusing. M42 mount lenses are insulated (normally) and don't short this pin, which is why they don't gove trap focus and focus confirmation.

As far as metering goes, and this applies to P-TTL flash and existing light photography with any camera past *istD. (OK I will refine this to be K10D, K20D, and K7D which I either have or know performance is the same). The *istD is the best most accurate camera I have seen for manual lenses. I have posted this data many times, therefore unless the camera knows the exact aperture of the lens that is mounted on it, the exposure will probably be wrong. This includes the K7, while better than K10D and K20D still suffers from exposure errors with manual aperture lenses.

While software can be implemented to do what you propose, assuming for example, the aperture activation can remain in the stopped down mode all the time, without damage (i.m not so sure) the other issues like adding a metering time between pressing the shutter release and tripping the shutter will make the shutter lag too long.

If you truely want reliable metering with flash for legacy lenses, use an *istD. It works just fine, in fact if you want pentax to address the legacy lenses, having dual mode flash, TTL/P-TTL like the *istD is the best way forward, and forget everything else you propose on flash because that is much simpler (although more expensive)

As for manual metering and stopped down mode, again, no matter what you do, the metering sucks shen compared to the *istD. I agree the K7 is better than the K10D/K20D but still much worse than *istD, and therefore the first thing pentax should do is allow you to enter maximum aperture, and then add for the green button exposure setting a 2 reading approach, wide open and stopped down, so they can apply the same compensation curve they use to your lens. That would make green button metering accurate for K and M lenses. After all, that's really all that is needed. For me, I much prefer the idea of having accurate metering as opposed to automated wrong metering with an increased shutter lag.

As for M42 lenses I don't understand at all your complaints.

Pentax DID change lens mounts, to advance their cameras, you are in one post bitching about the lack of backwards compatibility to a lens mount they abandoned 35 years ago, yet in another post stating that they should change mounts to avoid compatibility issues. Make up your mind.

At the end of the day, there are two things really that pentax should do here and one of them is not AV mode for K mounts.

They need to fix the metering with the green button by allowing entry of the open aperture of the lens, just like you enter for focal length, and they should provide and continue to offer TTL flash as well as P-TTL.